Got it. The mistake is in our code generation walk, which sets the level argument to default, whenever the from list is ("*",). A new test case, following one of Jim's excellent PEP 328 examples, fails that way. Now to work out what the logic ought to be at this point ... .

Jeff, re out-of-date class files, we handle this by a bytecode magic. The easiest way to see how updating the magic works is to look at a relevant commit: https://hg.python.org/jython/rev/ae190b66bf4c#l4.8, specifically incrementing the APIVersion by one

I didn't really see the bug-fix as an "API change". But I'll add that as it could conceivably bite a user. We're not close to running out of integers yet.
Playing with this, if having ensured my *$py.class files are old, then I hide the source x.py, the old Jython (API version matches x$py.class) runs, with the expected wrong result, while the new Jython (API version one up from x$py.class) says:
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: No module named x
rather than anything more nuanced about what really happened.
In comparable circumstances, CPython says:
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: Bad magic number in u\v\w\x.pyc
although I suppose that could be put better too.

Jeff, so our convention has been to update the APIVersion for any bytecode change that results in different behavior - including especially bug fixes. I think we still need to do this with subsequent releases in 2.7.x, especially since we want to open up opportunities for future optimization around generated bytecode.
Te specific ImportError message could be more nuanced, however. In cases like this I especially favor helpful diagnostic messages vs something terse.

I saw that. All the apparatus for better diagnosis is there in the code, but it was turned off (accidentally I assume) a long time ago.
But to be yet more helpful, I have changed the words to:
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: incompatible api version 36 (expected 37) in: u\v\w\x$py.class